System and method of mechanical compression refrigeration based on two-phase ejector

ABSTRACT

The present invention discloses the use of two-phase ejector(s) activated by pressurized refrigerant, said two-phase ejector(s) are strategically located in the cycle of the refrigeration system so as to provide part of the compression effect required for the refrigeration load, thereby relieving the conventional mechanical compressor from part of its duty, hence increasing the overall cycle efficiency of the refrigeration system.

FIELD OF THE INVENTION

The invention relates to system and method of mechanical compressionrefrigeration. In particular, the present invention discloses the use ofa two-phase ejector to improve efficiency and stability of mechanicalcompression refrigeration system.

BACKGROUND OF THE INVENTION

In recent years, technological advancements in the field of equipmentoptimization and controls have substantially reduced energy consumption.At the same time, the demand for increased comfort (for example, heatingand air-conditioning) or production of goods (for example, Agro-foodindustry), however, undermines these achievements by giving rise todemands for additional energy consumption. As a result, the overallcosts relating to energy consumption increase.

Estimations by research carried out by Natural Resources Canada indicatethat ten percent of total energy consumption in commercial,institutional and industrial activities relates to refrigeration.Refrigeration, or more generally, air conditioning, are no longer anoption but a requirement for daily consumptions, given the increasingdemand from consumers.

Currently, one of the solutions most investigated in improving energyefficiency in refrigeration involves the use of an ejector which may beintegrated into conventional refrigeration systems as internalcomponents in order to form hybrid cycles and improve performance. Anumber of these options are being considered in the current research(for example, cascades, hybrids, subcooling agents, ejecto-compressionor ejecto-absorption).

Some of these options, such as cascade and hybrid configurations, have agood potential for performance improvement and have been studiedtheoretically and experimentally at CanmetENERGY. They are typicallysuitable for low temperatures and medium to large capacities.

The refrigeration systems most currently used are based on mechanicalcompression. Electrically driven compressors are the main components insuch systems. Decent performance is generally obtained in such systems,which explains the popularity of this technology. However, lowtemperature refrigeration or heat pumping in cold conditions or airconditioning in a hot environment imposes a heavy load on the electricalgrid so that innovative ways of increasing efficiency and decreasingenergy consumption are sought.

Other than ejectors, other technologies based on heat activation (i.e.absorption, adsorption and chemical heat pumps) may also be available.However, they are complex, bulky and are not suitable alternatives tomechanical compression.

Mechanical based compression refrigeration becomes increasingly complexand consumes increasingly more electricity (noble energy) at high and/orlow temperature working conditions.

Therefore, there is the need for an efficient mechanical compressionrefrigeration system.

SUMMARY OF THE INVENTION

The objective of the present invention is to enhance the efficiency ofthe existing refrigeration cycles by assisting the compressor in arefrigeration system with a two-phase ejector activated by potentialenergy and available internal heat recovery.

According to one aspect of the invention, there is provided arefrigeration system, comprising:

-   -   a metering device for controlling flow of a refrigerant,    -   an evaporator,    -   means for supplying the refrigerant from the metering device        into the evaporator wherein the refrigerant evaporates into        vapor,    -   a two-phase ejector comprising means defining a liquid chamber        having a liquid inlet, means defining a vapor chamber having a        vapor inlet, and an outlet discharging a two-phase vapor-liquid        refrigerant stream,    -   means for supplying the vapor from the evaporator into the vapor        inlet of the two-phase ejector,    -   a flash tank compound separator,    -   means for supplying the refrigerant from the two-phase ejector        into the flash tank compound separator wherein the refrigerant        separates into two phases,    -   a compressor,    -   means for supplying the refrigerant from the flash tank compound        separator into the compressor wherein the refrigerant        compresses,    -   a condenser,    -   means for supplying the refrigerant from the compressor into the        condenser wherein the refrigerant condenses,    -   a receiver,    -   means for supplying the refrigerant from the condenser to the        receiver,    -   means for supplying the refrigerant from the receiver to the        liquid inlet of the two-phase ejector,    -   means for supplying the refrigerant from the receiver to the        metering device and then into the evaporator to start another        cycle through the system,    -   means for supplying the refrigerant from the flash tank compound        separator into a pump where the pressure of the refrigerant is        regulated,    -   means for supplying the refrigerant from the pump into the        receiver,    -   wherein the two-phase ejector then draws vapor from the        evaporator lifting its pressure to an intermediate level when        activated a mixture of condensate from the condenser and        subcooled refrigerant fed by the pump, and    -   wherein the pressure of the liquid inlet of the two-phase        ejector is controlled by the pump in accordance with the        operating conditions of the compressor.

According to another aspect of the invention, there is provided arefrigeration system, comprising:

-   -   a metering device for controlling flow of a refrigerant,    -   an evaporator,    -   means for supplying the refrigerant from the metering device        into the evaporator wherein the refrigerant evaporates into        vapor,    -   a two-phase ejector comprising means defining a liquid chamber        having a liquid inlet, means defining a vapor chamber having a        vapor inlet, and an outlet discharging a two-phase vapor-liquid        refrigerant stream,    -   means for supplying the vapor from the evaporator into the vapor        inlet of the two-phase ejector,    -   a flash tank compound separator,    -   means for supplying the refrigerant from the two-phase ejector        into the flash tank compound separator wherein the refrigerant        separates into two phases,    -   a compressor,    -   means for supplying the refrigerant from the flash tank compound        separator into the compressor wherein the refrigerant        compresses,    -   a condenser,    -   means for supplying the refrigerant from the compressor into the        condenser wherein the refrigerant condenses,    -   a heat exchanger,    -   means for supplying the refrigerant from the condenser to the        heat exchanger,    -   means for supplying the refrigerant from the heat exchanger to        the liquid inlet of the two-phase ejector,    -   means for supplying the refrigerant from the heat exchanger to        the metering device where the pressure and temperature of the        refrigerant decrease and then into the evaporator to start        another cycle through the system,    -   wherein the heat exchanger simultaneously increases condensate        subcooling at the inlet of metering device and decreases motive        liquid subcooling at the liquid inlet of two-phase ejector,    -   means for supplying the refrigerant from the flash tank compound        separator into a pump where the pressure of the refrigerant is        regulated,    -   means for supplying the refrigerant from the pump into the heat        exchanger,    -   wherein the two-phase ejector then draws vapor from the        evaporator lifting its pressure to an intermediate level when        activated a mixture of condensate from the condenser and        subcooled refrigerant fed by the pump, and    -   wherein the pressure of the liquid inlet of the two-phase        ejector is controlled by the pump in accordance with the        operating conditions of the compressor.

According to a further aspect of the invention, there is provided arefrigeration system, comprising:

-   -   a metering device for controlling flow of a refrigerant,    -   an evaporator,    -   means for supplying the refrigerant from the metering device        into the evaporator wherein the refrigerant evaporates into        vapor,    -   a two-phase ejector comprising means defining a liquid chamber        having a liquid inlet, means defining a vapor chamber having a        vapor inlet, and an outlet discharging a two-phase vapor-liquid        refrigerant stream,    -   means for supplying the vapor from the evaporator into the vapor        inlet of the two-phase ejector,    -   a flash tank compound separator, means for supplying the        refrigerant from the two-phase ejector into the flash tank        compound separator wherein the refrigerant separates into two        phases,    -   a compressor,    -   means for supplying the refrigerant from the flash tank compound        separator into the compressor wherein the refrigerant        compresses,    -   a condenser,    -   means for supplying the refrigerant from the compressor into the        condenser wherein the refrigerant condenses,    -   a mixing junction,    -   means for supplying the refrigerant from the condenser to the        mixing junction,    -   means for supplying the refrigerant from the mixing junction to        the liquid inlet of the two-phase ejector,    -   means for supplying the refrigerant from the flash tank compound        separator to the metering device where the pressure and        temperature of the refrigerant decrease and then into the        evaporator to start another cycle through the system,    -   means for supplying the refrigerant from the flash tank compound        separator into a pump,    -   means for supplying the refrigerant from the pump into the        mixing junction,    -   wherein the two-phase ejector then draws vapor from the        evaporator lifting its pressure to an intermediate level when        activated a mixture of condensate from the condenser and        subcooled refrigerant fed by the pump, and    -   wherein the pressure of the liquid inlet of the two-phase        ejector is controlled by the pump in accordance with the        operating conditions of the compressor.

According to one aspect of the invention, there is provided arefrigeration system, comprising:

-   -   a metering device for controlling flow of a refrigerant,    -   an evaporator,    -   means for supplying the refrigerant from the metering device        into the evaporator wherein the refrigerant evaporates into        vapor,    -   a two-phase ejector comprising means defining a liquid chamber        having a liquid inlet, means defining a vapor chamber having a        vapor inlet, and an outlet discharging a two-phase vapor-liquid        refrigerant stream,    -   means for supplying the vapor from the evaporator into the vapor        inlet of the two-phase ejector,    -   a flash tank compound separator,    -   means for supplying the refrigerant from the two-phase ejector        into the flash tank compound separator wherein the refrigerant        separates into two phases,    -   a compressor,    -   means for supplying the refrigerant from the flash tank compound        separator into the compressor wherein the refrigerant        compresses,    -   a condenser,    -   means for supplying the refrigerant from the compressor into the        condenser wherein the refrigerant condenses,    -   a heat exchanger,    -   means for supplying the refrigerant from the condenser to the        heat exchanger,    -   means for supplying the refrigerant from the compressor to the        heat exchanger,    -   a first valve for controlling the supply of the refrigerant from        the compressor to the condenser and a second valve for        controlling the supply of the refrigerant from the compressor to        the heat exchanger;    -   wherein by controlling and adjusting the first and/or the second        valve, the heat exchanger transfers part of condensation heat of        the compressed vapor to subcooled compressed liquid circulated        by pump to the two-phase ejector,    -   means for supplying the refrigerant from the heat exchanger to        the liquid inlet of the two-phase ejector,    -   means for supplying the refrigerant from the heat exchanger to        the metering device where the pressure and temperature of the        refrigerant decrease and then into the evaporator to start        another cycle through the system,    -   wherein the heat exchanger simultaneously increases condensate        subcooling at the inlet of metering device and decreases motive        liquid subcooling at the liquid inlet of two-phase ejector,    -   means for supplying the refrigerant from the flash tank compound        separator into a pump where the pressure of the refrigerant is        regulated,    -   means for supplying the refrigerant from the pump into the heat        exchanger,    -   wherein the two-phase ejector then draws vapor from the        evaporator lifting its pressure to an intermediate level when        activated a mixture of condensate from the condenser and        subcooled refrigerant fed by the pump, and    -   wherein the pressure of the liquid inlet of the two-phase        ejector is controlled by the pump in accordance with the        operating conditions of the compressor.

According to one aspect of the invention, there is provided arefrigeration system, comprising:

-   -   a metering device for controlling flow of a refrigerant,    -   an evaporator,    -   means for supplying the refrigerant from the metering device        into the evaporator wherein the refrigerant evaporates into        vapor,    -   a two-phase ejector comprising means defining a liquid chamber        having a liquid inlet, means defining a vapor chamber having a        vapor inlet, and an outlet discharging a two-phase vapor-liquid        refrigerant stream,    -   means for supplying the vapor from the evaporator into the vapor        inlet of the two-phase ejector,    -   a flash tank compound separator,    -   means for supplying the refrigerant from the two-phase ejector        into the flash tank compound separator wherein the refrigerant        separates into two phases,    -   a compressor,    -   means for supplying the refrigerant from the flash tank compound        separator into the compressor wherein the refrigerant        compresses,    -   a condenser,    -   means for supplying the refrigerant from the compressor into the        condenser wherein the refrigerant condenses,    -   a direct contact condenser,    -   means for supplying the refrigerant from the condenser to the        direct contact condenser,    -   means for supplying the refrigerant from the compressor to the        direct contact condenser,    -   a first valve for controlling the supply of the refrigerant from        the compressor to the condenser and a second valve for        controlling the supply of the refrigerant from the compressor to        the direct contact condenser;    -   wherein by controlling and adjusting the first and/or the second        valve, the direct contact condenser transfers part of        condensation heat of the compressed vapor to subcooled        compressed liquid circulated by pump to the two-phase ejector,    -   means for supplying the refrigerant from the direct contact        condenser to the liquid inlet of the two-phase ejector,    -   means for supplying the refrigerant from the flash tank compound        separator to the metering device where the pressure and        temperature of the refrigerant decrease and then into the        evaporator to start another cycle through the system,    -   means for supplying the refrigerant from the flash tank compound        separator into a pump where the pressure of the refrigerant is        regulated,    -   means for supplying the refrigerant from the pump into the        direct contact condenser,    -   wherein the two-phase ejector then draws vapor from the        evaporator lifting its pressure to an intermediate level when        activated a mixture of condensate from the condenser and        subcooled refrigerant fed by the pump, and    -   wherein the pressure of the liquid inlet of the two-phase        ejector is controlled by the pump in accordance with the        operating conditions of the compressor.

Preferably, the metering device is a thermal expansion valve, or acapillary tube.

Preferably, refrigerant used in the refrigeration system is carbondioxide.

Other features and advantages of the present invention will becomeapparent from the following detailed description and the accompanyingdrawings, which illustrate, by way of example, the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, preferred embodiments of the present inventionare described hereinafter with reference to the accompanying drawings,wherein:

FIG. 1 is a schematic representation of an embodiment of a conventionalrefrigeration cycle (prior art);

FIG. 2 is a schematic representation of an embodiment of a two-phaseejector assisted mechanical refrigeration cycle according to the presentinvention;

FIG. 3 is a schematic representation of a second embodiment of atwo-phase ejector assisted mechanical refrigeration cycle according tothe present invention;

FIG. 4 is a schematic representation of a third embodiment of atwo-phase ejector assisted mechanical refrigeration cycle according tothe present invention;

FIG. 5 is a schematic representation of a fourth embodiment of atwo-phase ejector assisted mechanical refrigeration cycle according tothe present invention; and

FIG. 6 is a schematic representation of a fifth embodiment of atwo-phase ejector assisted mechanical refrigeration cycle according tothe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Mechanical refrigeration is the utilization of mechanical componentsarranged in a “refrigeration system” for the purpose of transferringheat. The refrigeration cycle is based on the well-known physicalprinciple that a liquid evaporating into a gas extracts heat from thesurrounding area. The refrigeration cycle is to remove unwanted heatfrom one place and discharge it into another. To accomplish this, therefrigerant is pumped through a closed refrigeration system.

Refrigerants are chemical compounds that are alternately compressed andcondensed into a liquid and then permitted to expand and to evaporateinto a vapor or gas as they are pumped through the mechanicalrefrigeration system to cycle. Refrigerants evaporate at much lowertemperatures than water, which permits them to extract heat at lowertemperature than water.

Two different pressures exist in the cycle—the evaporating or lowpressure in the “low side,” and the condensing, or high pressure, in the“high side.” These pressure areas are separated by two dividing points:one is the metering device where the refrigerant flow is controlled, andthe other is at the compressor, where vapor is compressed.

Referring to FIG. 1, a schematic representation of an embodiment of anexisting conventional refrigeration cycle system 1, a metering device 5may be a thermal expansion valve, a capillary tube, or any other deviceto control the flow of refrigerant into an evaporator 6, or coolingcoil, as a low-pressure, low-temperature refrigerant. The expandingrefrigerant evaporates as it goes through evaporator 6, where it removesthe heat from the substance or space in which evaporator 6 is located.Heat travels from the warmer substance to evaporator 6 cooled by theevaporation of the refrigerant within the system, causing therefrigerant to evaporate to a vapor. This low-pressure, low-temperaturevapor is then drawn to a compressor 7 where the low-temperature vapor iscompressed into a high-temperature, high-pressure vapor. Compressor 7then discharges the high-temperature, high-pressure vapor to a condenser8. The high-temperature, high-pressure refrigerant vapor is at a highertemperature than the air or water passing across the condenser,therefore heat is transferred to the cooler air or water. As heat isremoved from the vapor, the vapor is condensed into a liquid, at ahigh-pressure. The liquid refrigerant travels to metering device 5 whereit passes through a small opening or orifice where a drop in pressureand temperature occurs, and then it enters into evaporator 6. As therefrigerant makes its way into the large opening of the evaporatortubing or coil, it vaporizes, ready to start another cycle through thesystem.

An ejector is a device in which two streams flow in intimate contact atrelatively high velocity such that the driving stream transfers momentumto the driven stream, thereby increasing the stagnation pressure of thedriven stream. The two streams are accelerated in separate nozzles toapproximately the same pressure before being brought together in amixing section and the mixed stream is decelerated in a diffuser. Anejector can be used to generate isentropic condition in the throttlingprocess. Because the phase of the working fluid in the diffuser is a twophase, an ejector is usually named as two-phase ejector.

In the present invention, two-phase ejector(s) activated by pressurizedrefrigerant are used and strategically located in the cycle of therefrigeration system so as to provide part of the compression effectrequired for the refrigeration load, thereby relieving the conventionalmechanical compressor from part of its duty, hence increasing theoverall cycle efficiency of the refrigeration system.

The two-phase ejectors are pressure-activated. In a mechanicalrefrigeration cycle, the two-phase ejectors can recover internal energyotherwise wasted, in order to produce a modest compression effect, apseudo-isentropic expansion and an appreciable refrigerant circulatoryeffect. The two-phase ejectors can be integrated therefore in amechanical compression system to produce improved cooling orrefrigeration of the conventional cycle.

Unlike conventional mechanical compressors, the two-phase ejectors arestatic mechanical components; they are compact, flexible, simple and lowcost.

In its function, the two-phase ejector contributes to the overallcompression so that conventional mechanical compressor's work isreduced, and its efficiency improved, resulting in overall improvedcycle performance.

Because two-phase ejectors are static and compact components,modification to the conventional refrigeration cycle to incorporate thetwo-phase ejectors introduces no major and/or costly changes but resultsin substantial performance gains.

According to the present invention, the two-phase ejector does notcompletely replace the conventional mechanical compressor but serves tobuild a new cycle arrangement in which the conventional mechanicalcompressor and the two-phase ejector can fulfill their respective dutiesof fluid circulation and compression without or with minimalinterference.

According to the present invention, the two-phase ejector is placed inseries with the conventional mechanical compressor to the suction ofwhich it feeds refrigerant drawn from the evaporator, but it isactivated independently from the conventional mechanical compressor.

The two-phase ejector and conventional mechanical compressor assemblyforms a hybrid system which uses a common refrigerant to bothcomponents.

In existing prior art refrigeration systems, either:

-   -   (1) the two-phase ejector completely replaces the conventional        mechanical compressor which is then replaced by a pump; or    -   (2) the two-phase ejector and the conventional mechanical        compressor are arranged in series in such a way that the ejector        is activated by the conventional mechanical compressor via the        condensate and in turn the two-phase ejector feeds the        conventional mechanical compressor in vapor via the evaporator.

In these types of existing setups, it is obvious that both the two-phaseejector and the conventional mechanical compressor are strongly coupled,therefore preventing their stable operation.

In contrast, the refrigeration cycle options described in the presentinvention hybrid the two-phase ejector and conventional mechanicalcompressor configurations. Their main features are summarized below.

In FIG. 2, an embodiment of a two-phase ejector assisted mechanicalrefrigeration system 10 consists of a cycle in which a two-phase ejector11 and a flash tank compound separator (or a second reservoir) 12 arepositioned sequentially between a receiver (or the first fluiddistribution reservoir) 9 and a compressor 7. Part of the liquid inreceiver 9 is expanded through metering device 5 to the conditions ofevaporator 6. The two-phase ejector 11 draws vapor from evaporator 6lifting its pressure to an intermediate level when activated a mixtureof condensate and subcooled refrigerant fed by a pressure pump 13.Therefore, adequate subcooling of the two-phase ejector feed and theevaporator can be adjusted for optimal operation. This combinationminimizes the detrimental coupling of two-phase ejector 11 andcompressor 7 and results in improved cycle stability and performance.The two-phase ejector 11 and compressor 7 are in series and are alwaysboth in operation. The system uses one refrigerant and is suitable for awide range of applications and capacities.

FIG. 3 depicts another embodiment of a two-phase ejector assistedmechanical refrigeration system 20, which is a variant of system 10 asdescribed in FIG. 2.

In FIG. 3, receiver (or the first fluid distribution reservoir) 9 inFIG. 2 is replaced by a compact heat exchanger 21, which allows for moreoperational flexibility. This measure simultaneously increasescondensate subcooling at the inlet of metering device (expansion valve)5 and decreases motive liquid subcooling at the primary inlet oftwo-phase ejector 11, which improve the overall cycle performance. Inaddition, the primary inlet pressure of two-phase ejector 11 iscontrolled by pump 13 independently of the pressure of condenser 8.

FIG. 4 depicts another embodiment of a two-phase ejector assistedmechanical refrigeration system 30, which is a variant of system 10 and20 as depicted in FIGS. 2 and 3, respectively.

In FIG. 4, evaporator 6 is fed by the refrigerant from flash tankcompound separator (or a second reservoir) 12 at intermediate pressure;and receiver (or the first fluid distribution reservoir) 9 in FIG. 2 isreplaced by a mixing junction 31. This configuration simplifies thecycle of the refrigeration system further by the removal of a vessel,therefore reducing expansion losses in evaporator 6.

FIG. 5 represents an additional embodiment of a two-phase ejectorassisted mechanical refrigeration system 40 wherein the condenser 8 ispartially replaced by a heat exchanger 21, achieved by controllingvalves 42 (valve 42 a for controlling the supply of the refrigerant fromcompressor 7 to condenser 8 and/or valve 42 b for controlling the supplyof the refrigerant from compressor 7 to heat exchanger 21) and depend onthe expansion extent and quality in the nozzle of two-phase ejector 11;the other components remaining unchanged.

In this case, heat exchanger 21 transfers a variable part of thecondensation heat of the compressed vapor to the highly subcooledcompressed liquid circulated by pump 13 to two-phase ejector 11. Thisprocess has, inter alia, the following advantages:

-   -   By condensing part of the compression vapor, the size of        condenser 8 will be substantially reduced;    -   The two-phase ejector 11 subcooled inlet conditions can be        adjusted to maximize its efficiency;    -   The level of heat rejection can be varied to maximize the        efficiency of compressor 7 and maximize overall performance of        the system, particularly when condenser 8 is less needed; and    -   Where condenser 8 is fully used, two-stage compressor and        multi-circuit heat exchanger may be contemplated to divert only        minimal stream to condenser 8 in order for the compressor 7 to        operate with minimal consumption.

FIG. 6 depicts another embodiment of a two-phase ejector assistedmechanical refrigeration system 50, which is a variant of system 40 asdescribed in FIG. 5.

In FIG. 6, the heat exchanger 21 in FIG. 5 is replaced by a moreefficient and direct contact condenser 55 and an evaporator feed fromintermediate pressure flash tank compound separator (or a secondreservoir) 12 to further reduce expansion losses.

Any of the configurations as described above may use any of therefrigerants currently available.

Preferably, carbon dioxide (CO₂) is more suitable for the intendedtwo-phase ejector refrigeration/heat pump operation.

Preferably, the metering device is a thermal expansion valve, or acapillary tube.

Although the present invention has been described in considerable detailwith reference to certain preferred embodiments thereof, otherembodiments and modifications are possible. Therefore, the scope shouldnot be limited by the preferred embodiments set forth in theafore-mentioned illustrative examples but should be given the broadestinterpretation consistent with the description as a whole.

1. A refrigeration system, comprising: a metering device for controllingflow of a refrigerant, an evaporator, means for supplying therefrigerant from the metering device into the evaporator wherein therefrigerant evaporates into vapor, a two-phase ejector comprising meansdefining a liquid chamber having a liquid inlet, means defining a vaporchamber having a vapor inlet, and an outlet discharging a two-phasevapor-liquid refrigerant stream, means for supplying the vapor from theevaporator into the vapor inlet of the two-phase ejector, a flash tankcompound separator, means for supplying the refrigerant from thetwo-phase ejector into the flash tank compound separator wherein therefrigerant separates into two phases, a compressor, means for supplyingthe refrigerant from the flash tank compound separator into thecompressor wherein the refrigerant compresses, a condenser, means forsupplying the refrigerant from the compressor into the condenser whereinthe refrigerant condenses, a receiver, means for supplying therefrigerant from the condenser to the receiver, means for supplying therefrigerant from the receiver to the liquid inlet of the two-phaseejector, means for supplying the refrigerant from the receiver to themetering device and then into the evaporator to start another cyclethrough the system, means for supplying the refrigerant from the flashtank compound separator into a pump where the pressure of therefrigerant is regulated, means for supplying the refrigerant from thepump into the receiver, wherein the two-phase ejector then draws vaporfrom the evaporator lifting its pressure to an intermediate level whenactivated a mixture of condensate from the condenser and subcooledrefrigerant fed by the pump, and wherein the pressure of the liquidinlet of the two-phase ejector is controlled by the pump in accordancewith the operating conditions of the compressor.
 2. A refrigerationsystem, comprising: a metering device for controlling flow of arefrigerant, an evaporator, means for supplying the refrigerant from themetering device into the evaporator wherein the refrigerant evaporatesinto vapor, a two-phase ejector comprising means defining a liquidchamber having a liquid inlet, means defining a vapor chamber having avapor inlet, and an outlet discharging a two-phase vapor-liquidrefrigerant stream, means for supplying the vapor from the evaporatorinto the vapor inlet of the two-phase ejector, a flash tank compoundseparator, means for supplying the refrigerant from the two-phaseejector into the flash tank compound separator wherein the refrigerantseparates into two phases, a compressor, means for supplying therefrigerant from the flash tank compound separator into the compressorwherein the refrigerant compresses, a condenser, means for supplying therefrigerant from the compressor into the condenser wherein therefrigerant condenses, a heat exchanger, means for supplying therefrigerant from the condenser to the heat exchanger, means forsupplying the refrigerant from the heat exchanger to the liquid inlet ofthe two-phase ejector, means for supplying the refrigerant from the heatexchanger to the metering device where the pressure and temperature ofthe refrigerant decrease and then into the evaporator to start anothercycle through the system, wherein the heat exchanger simultaneouslyincreases condensate subcooling at the inlet of metering device anddecreases motive liquid subcooling at the liquid inlet of two-phaseejector, means for supplying the refrigerant from the flash tankcompound separator into a pump where the pressure of the refrigerant isregulated, means for supplying the refrigerant from the pump into theheat exchanger, wherein the two-phase ejector then draws vapor from theevaporator lifting its pressure to an intermediate level when activateda mixture of condensate from the condenser and subcooled refrigerant fedby the pump, and wherein the pressure of the liquid inlet of thetwo-phase ejector is controlled by the pump in accordance with theoperating conditions of the compressor.
 3. A refrigeration system,comprising: a metering device for controlling flow of a refrigerant, anevaporator, means for supplying the refrigerant from the metering deviceinto the evaporator wherein the refrigerant evaporates into vapor, atwo-phase ejector comprising means defining a liquid chamber having aliquid inlet, means defining a vapor chamber having a vapor inlet, andan outlet discharging a two-phase vapor-liquid refrigerant stream, meansfor supplying the vapor from the evaporator into the vapor inlet of thetwo-phase ejector, a flash tank compound separator, means for supplyingthe refrigerant from the two-phase ejector into the flash tank compoundseparator wherein the refrigerant separates into two phases, acompressor, means for supplying the refrigerant from the flash tankcompound separator into the compressor wherein the refrigerantcompresses, a condenser, means for supplying the refrigerant from thecompressor into the condenser wherein the refrigerant condenses, amixing junction, means for supplying the refrigerant from the condenserto the mixing junction, means for supplying the refrigerant from themixing junction to the liquid inlet of the two-phase ejector, means forsupplying the refrigerant from the flash tank compound separator to themetering device where the pressure and temperature of the refrigerantdecrease and then into the evaporator to start another cycle through thesystem, means for supplying the refrigerant from the flash tank compoundseparator into a pump, means for supplying the refrigerant from the pumpinto the mixing junction, wherein the two-phase ejector then draws vaporfrom the evaporator lifting its pressure to an intermediate level whenactivated a mixture of condensate from the condenser and subcooledrefrigerant fed by the pump, and wherein the pressure of the liquidinlet of the two-phase ejector is controlled by the pump in accordancewith the operating conditions of the compressor.
 4. A refrigerationsystem, comprising: a metering device for controlling flow of arefrigerant, an evaporator, means for supplying the refrigerant from themetering device into the evaporator wherein the refrigerant evaporatesinto vapor, a two-phase ejector comprising means defining a liquidchamber having a liquid inlet, means defining a vapor chamber having avapor inlet, and an outlet discharging a two-phase vapor-liquidrefrigerant stream, means for supplying the vapor from the evaporatorinto the vapor inlet of the two-phase ejector, a flash tank compoundseparator, means for supplying the refrigerant from the two-phaseejector into the flash tank compound separator wherein the refrigerantseparates into two phases, a compressor, means for supplying therefrigerant from the flash tank compound separator into the compressorwherein the refrigerant compresses, a condenser, means for supplying therefrigerant from the compressor into the condenser wherein therefrigerant condenses, a heat exchanger, means for supplying therefrigerant from the condenser to the heat exchanger, means forsupplying the refrigerant from the compressor to the heat exchanger, afirst valve for controlling the supply of the refrigerant from thecompressor to the condenser and a second valve for controlling thesupply of the refrigerant from the compressor to the heat exchanger;wherein by controlling and adjusting the first and/or the second valve,the heat exchanger transfers part of condensation heat of the compressedvapor to subcooled compressed liquid circulated by pump to the two-phaseejector, means for supplying the refrigerant from the heat exchanger tothe liquid inlet of the two-phase ejector, means for supplying therefrigerant from the heat exchanger to the metering device where thepressure and temperature of the refrigerant decrease and then into theevaporator to start another cycle through the system, wherein the heatexchanger simultaneously increases condensate subcooling at the inlet ofmetering device and decreases motive liquid subcooling at the liquidinlet of two-phase ejector, means for supplying the refrigerant from theflash tank compound separator into a pump where the pressure of therefrigerant is regulated, means for supplying the refrigerant from thepump into the heat exchanger, wherein the two-phase ejector then drawsvapor from the evaporator lifting its pressure to an intermediate levelwhen activated a mixture of condensate from the condenser and subcooledrefrigerant fed by the pump, and wherein the pressure of the liquidinlet of the two-phase ejector is controlled by the pump in accordancewith the operating conditions of the compressor.
 5. A refrigerationsystem, comprising: a metering device for controlling flow of arefrigerant, an evaporator, means for supplying the refrigerant from themetering device into the evaporator wherein the refrigerant evaporatesinto vapor, a two-phase ejector comprising means defining a liquidchamber having a liquid inlet, means defining a vapor chamber having avapor inlet, and an outlet discharging a two-phase vapor-liquidrefrigerant stream, means for supplying the vapor from the evaporatorinto the vapor inlet of the two-phase ejector, a flash tank compoundseparator, means for supplying the refrigerant from the two-phaseejector into the flash tank compound separator wherein the refrigerantseparates into two phases, a compressor, means for supplying therefrigerant from the flash tank compound separator into the compressorwherein the refrigerant compresses, a condenser, means for supplying therefrigerant from the compressor into the condenser wherein therefrigerant condenses, a direct contact condenser, means for supplyingthe refrigerant from the condenser to the direct contact condenser,means for supplying the refrigerant from the compressor to the directcontact condenser, a first valve for controlling the supply of therefrigerant from the compressor to the condenser and a second valve forcontrolling the supply of the refrigerant from the compressor to thedirect contact condenser; wherein by controlling and adjusting the firstand/or the second valve, the direct contact condenser transfers part ofcondensation heat of the compressed vapor to subcooled compressed liquidcirculated by pump to the two-phase ejector, means for supplying therefrigerant from the direct contact condenser to the liquid inlet of thetwo-phase ejector, means for supplying the refrigerant from the flashtank compound separator to the metering device where the pressure andtemperature of the refrigerant decrease and then into the evaporator tostart another cycle through the system, means for supplying therefrigerant from the flash tank compound separator into a pump where thepressure of the refrigerant is regulated, means for supplying therefrigerant from the pump into the direct contact condenser, wherein thetwo-phase ejector then draws vapor from the evaporator lifting itspressure to an intermediate level when activated a mixture of condensatefrom the condenser and subcooled refrigerant fed by the pump, andwherein the pressure of the liquid inlet of the two-phase ejector iscontrolled by the pump in accordance with the operating conditions ofthe compressor.
 6. The refrigeration system according to any one ofclaims 1 to 5, wherein the metering device is a thermal expansion valve,or a capillary tube.
 7. The refrigeration system according to any one ofclaims 1 to 6, wherein the refrigerant is carbon dioxide.